Ball valve - does flow direction matter?

[ILikeRust]

Thanks to Maine Sail's excellent tutorial on replacing through-hulls, I soon will be doing this job per his instructions.

As he recommends, I bought the Groco flanged adapter and ball valve and a bronze "mushroom" through-hull fitting.

The valve I bought is the same as the one shown here.

I notice that the valve body is not symmetrical in its construction - it appears that it can be disassembled. This leads me to suspect that it might be designed to have the water flow through it in one direction only - although there is no arrow or other marking on it to indicate this.

So - anybody know whether it matters? I've done a little Googling of the issue, and evidently there are some ball valves that are in fact unidirectional. I just need to know if this is one of them - and if so, which way does the flow have to go?

Thanks!

[gosolar]

From what I see in the pic this valve has a drain screw. It should be mounted so that whatever the valve controls can be drained. Going back to the pic it is mounted in the correct position. If it is at all possible put the drain screw at the bottom or to either side. eg. If the valve is on the water system and you need to work on it then it can be drained without having to remove the hoses from the valve.

[jstaff]

There are ball valves that release the pressure form the downstream side when closed, but besides that, I'm not familiar with there being a flow direction. What you see as being able to be "disassembled" is just part of its machining and assembly. I've never know of there being any reworking of ball valves. Large globe and gate valves are rebuilt routinely.

Since the ball valve is not intended to be "throttled" or adjusted (like a globe valve) flow direction is not an issue.

[ILikeRust]

Yup, I realized after posting this that the drain screw is the key.

Here is the page from the Groco on-line catalog showing this valve assembled to the flanged adapter.

I figure if the catalog shows it mounted that way, that must be the correct orientation. But I also note that this is the reverse of how Maine Sail shows it mounted.

[jstaff]

The nice thing about not having a drain is that you don't need to worry about the plug...

Usually on a pleasure boat you need to drain the entire line anyway.

I would have the drain to the inboard side. If it fails you only have the contents of your system to leak out; instead of the raw water sinking your boat.